Semiconductor devices as one type of the object of measurement or inspection by the scanning electron microscope are becoming increasingly miniaturized, requiring ever higher resolution from the scanning electron microscope. Patent Literature 1 discloses a monochromator that enables an increase in resolution. The monochromator disperses the energy of an electron beam, and selectively acquires electrons having specific energy, thus making it possible to render the beam monochromatic. Patent Literature 2 discloses a scanning electron microscope including a multiple prisms chain disposed in the beam path for aberration suppression. The microscope detects secondary electrons separated from the electron beam trajectory by utilizing the deflecting action of the multiple prism chain.